[Repo Assist] perf(rust-guard): add ORDER_LOW_TO_HIGH_PIPED const and direct tests for parse_integrity/scope_string

[github-actions]

🤖 This PR was created by Repo Assist, an automated AI assistant.

Root Cause

parse_integrity in lib.rs built an error message string at runtime via a 7-step iterator chain:

policy_integrity::ORDER_HIGH_TO_LOW
    .iter()
    .rev()
    .copied()
    .collect::<Vec<_>>()
    .join("|")

This allocates a temporary Vec<&str> and a heap String each time an invalid min-integrity value is supplied, even though the result is the compile-time constant "none|unapproved|approved|merged".

Additionally, parse_integrity and scope_string had no direct unit tests — they were only covered indirectly through integration tests, leaving the error message text and None-fallback arms of scope_string unverified.

Changes

guards/github-guard/rust-guard/src/labels/constants.rs

• Added ORDER_LOW_TO_HIGH_PIPED: &str = "none|unapproved|approved|merged" to the policy_integrity module — a compile-time constant replacing the runtime chain.
• Added order_low_to_high_piped_matches_order_high_to_low: a consistency test that derives the piped string from ORDER_HIGH_TO_LOW at test time and asserts it equals ORDER_LOW_TO_HIGH_PIPED, preventing silent drift if integrity levels are ever added or reordered.

guards/github-guard/rust-guard/src/lib.rs

• Replaced the 7-step iterator chain in parse_integrity with policy_integrity::ORDER_LOW_TO_HIGH_PIPED.
• Added parse_integrity_accepts_all_valid_values: verifies all four valid tokens are accepted.
• Added parse_integrity_rejects_unknown_value: verifies the error message contains the full ORDER_LOW_TO_HIGH_PIPED constant string (not just individual tokens), locking down the exact error message content.
• Added scope_string_all_arms: covers all 8 ScopeKind arms including None-fallback cases for Owner/Repo/RepoPrefix.

Test Status

Rust tests: ✅ 387/387 passed (cargo test in guards/github-guard/rust-guard/)

Go build/tests: ⚠️ Infrastructure issue — go 1.25.0 toolchain download blocked by network firewall (proxy.golang.org forbidden). No Go files were changed.

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[Copilot]

Pull request overview

This PR improves the Rust GitHub guard’s policy parsing by removing a runtime allocation-heavy iterator chain from parse_integrity’s error message construction, replacing it with a compile-time constant, and adding direct unit tests for parse_integrity and scope_string to cover previously untested branches.

Changes:

• Added policy_integrity::ORDER_LOW_TO_HIGH_PIPED as a compile-time "none|unapproved|approved|merged" string.
• Updated parse_integrity to use the new constant instead of building the string via iterator/allocations.
• Added focused unit tests for parse_integrity (valid + invalid) and scope_string (all match arms).

Show a summary per file

File	Description
guards/github-guard/rust-guard/src/lib.rs	Uses the new const for parse_integrity error formatting; adds direct unit tests for parse_integrity and scope_string.
guards/github-guard/rust-guard/src/labels/constants.rs	Introduces ORDER_LOW_TO_HIGH_PIPED constant for integrity option formatting.

Copilot's findings

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• Files reviewed: 2/2 changed files
• Comments generated: 2

[lpcox]

@copilot address the review feedback and fix this ci check https://github.com/github/gh-aw-mcpg/actions/runs/25673919245/job/75366898011?pr=5468

[Copilot]

@copilot address the review feedback and fix this ci check https://github.com/github/gh-aw-mcpg/actions/runs/25673919245/job/75366898011?pr=5468

Done in commit fix(rust-guard): fix dead-code CI error; strengthen consistency and error-message tests per review.

CI failure: ORDER_HIGH_TO_LOW had no remaining usages after the previous change, triggering a -D dead-code compile error. Fixed by adding a test that uses it.

Review feedback addressed:

• constants.rs: added order_low_to_high_piped_matches_order_high_to_low — derives the piped string from ORDER_HIGH_TO_LOW at test time and asserts it equals ORDER_LOW_TO_HIGH_PIPED, preventing silent drift if integrity levels change.
• lib.rs: strengthened parse_integrity_rejects_unknown_value to assert the full policy_integrity::ORDER_LOW_TO_HIGH_PIPED constant appears in the error message, rather than just checking for individual tokens.

All 387 Rust tests pass.